Update Node version

[genehack]

We're currently running Node v20 — ^20 per package.json:engines.node, v20.9 per .nvmrc. Per Node's endoflife.date page, active support for this version ended in October; security updates will stop in 9 months.

Migrating to v24 now would get us around a year of active support.

(Maybe we could get crazy and do something about this as part of the same effort:

62 vulnerabilities (8 low, 14 moderate, 30 high, 10 critical)

)